Process for purifying, enriching, or refining crude graphite



I Patented Jan. 11, 1 927.

EDMOND JEAN EUGENE DUMOND, OF PARIS, FRANCE. I

rnoonss non romrvme, ENRICHING, on nnrmme CRUDE swarm.

No Drawing. Application filed April 8, 1925, Serial No. 21,701, and in France April 83, 1924.

Lumps or flakes of graphite are, as is well known, generally made up from a series of smaller flakes or fragments of pure graphite in aggregations united together by a silicious 5 or alummous cement.

It follows that in order to purify or refine the mineral, it is necessary to employ a process for eliminating the largest possible proportion of the sillcious or aluminous cement, whilst leaving the pure graphite in its original physical state, that is to say in the form of line particles in which it existed when united in the coarser lumps submitted to treatment. The present process has for its object the enrichment or refining of graphite by subimttmg the mineral to various treatments in succession, namely in the first place to a process of crushing then to tritur'ation in a damp state in a tube mill or apparatus, then to separation in the damp state. by sitting or passing through a sieve, and finally to flotation for the purpose of separating out the fine'particles of refined graphite, those a; which are coarsest being again passed to the refining apparatus and again washed and sieved and floated in order to increase their richness or purity.

The trituration of the mineral, which has been previously crushed for; instance to such a degree as to enable it to pass through a number 6 mesh, is efi'ectedin a tube mill or apparatus, the triturating means comprising metallic coned elements, sufiioient-Waterbea ing injected at the timeof treatment to render. the mixture pasty. The object of this operation is to liberate or separate the constituentelements of the original lump or flake. The cementing material ot the to graphite particles is finely crushed, whilst the-small fragments of graphite, 'byreason oftheir slimy nature remain almost unaffected. i l J Consequently, at the end of the treatment to in the crushing apparatusjthere is obtained amixture consisting of ellicles of graphite, and silica, alumina and oxide of iron in a very finely pulverizedcondition, and'these.

it is necessary to separate. I0 Thesieving'or sitting of thematenal 1s efi'ected by means of a pneumatic vibrating sieve provided with a metallic net, of greater or less fineness, an atom zer or spray pro-' rated.

ducer being employed for constantly spraying with water the material under treatment, which increases to a considerable extent the eilicacy of the sieving or sitting.

The two classes of material or products classified by the foregoing process are then passed to flotation chambers.

In this Way graphite is obtained containing from to 92% of carbon graphite of very high lubricating power. The graphite may be obtained of various degrees of coarseness, passing for example through 60, 120 or 200 mesh sieves.

The material which is coarser than 120 -mesh is passed again through'the crushing apparatus through the washer and through the flotation chambers, which gives a graphite of a greater purity than 95%.

If desired an even greater-percentage of purity may be obtained by chemical treatnient.

For this purpose the graphite obtained as (I above described is mixed with a determined proportion by weight of carbonate of soda according to the ganguecontent to be sepa- The mixture is raised to 700 in a gas heated continuous kiln, and the operation may then be carriedout in either of the two following methods (a) The product obtained from the kiln is passed again to the tube mill or apparatus and then may be sieved in the wet state and treated by flotation as explained above. (b) If hydrochloric-acid is obtainable ata commercial rate the material may be treated with a quantity of dilute acid sufiicient for the soluble products, thus separating them together with silica in an extremely finely divided state. By washing, the soluble products and any excess of acid are removed, and the resulting material is sieved or sifted by means of the pneumatic vibrator to separate out the silica.

By these two processes graphite of a p i'ity up to 99 or 99.5% is obtained.

I claim:

1. The art of refining graphite, comprising crushing the crude graphite, grinding the product wet, sitting the ground material 7 while subjected to as ray of'water, 'separating the graphite an chemically treating the sifted graphite for removal of residual 10' gangue.

2. In the art of refining: graphite, mixing artially refined graphite with sodium caronate, heating the mixture to fusion and grinding the product Wet.

3. In the art of refining graphite, mixing artia'lly refined graphite with sodium caronate, fusing the same, grinding the prod- 

